\begin{table}%t1
\caption{\label{calib}Calibration stars used, together with their 
USNO-A2.0 derived magnitudes.}
%\centering
  \small \begin{tabular}{lcclc}
\hline\hline \noalign{\smallskip}
$id$ &       $mag$    & \qquad & $id$ &        $mag$    \\
\hline
1    & $14.203\pm0.001$ &        & 5    &  $15.854\pm0.006$ \\
2    & $16.602\pm0.010$ &        & 6    &  $15.980\pm0.006$ \\
3    & $16.689\pm0.011$ &        & 7    &  $17.139\pm0.015$ \\
4    & $16.012\pm0.007$ &        & 8    &  $17.185\pm0.018$ \\
\hline
\end{tabular}
\end{table}